1. Field of the Invention
This invention relates to an electronic controlled stitch pattern sewing machine for sewing a stitch pattern on a workpiece based on stitch pattern data previously stored in a memory.
2. Prior art
Various types of stitch pattern sewing machine have been proposed as prior arts. For example, electronic controlled stitch pattern sewing machines have been disclosed in U.S. Pat. Nos. 4,388,884 and 4,413,574. In these arts, the sewing machine is equipped with a memory device for storing stitch pattern data assigned by X-Y coordinates corresponding to each of patterns such as letters and symbols to be sewn, and is also provided with a keyboard for selecting desired patterns from the stitch pattern data stored in the memory and for determining the size and the arrangement of the selected patterns. Moreover, the sewing machine has a function to determine whether or not the arranged patterns can fit within a predetermined sewing region confined by an embroidery frame. If they do not fit within the predetermined sewing region, a warning is given to the operator in advance so that a collision between the needle and the embroidery frame can be prevented.
These prior arts, however, include some shortcomings. For the purpose of sewing operation which is sewing the stitch patterns from one end of the extent of desired sewing region to the other end thereof, the operator is required to calculate an enlargement ratio or a contraction ratio of the patterns to make the size of the patterns close to that of the desired sewing region. Moreover, in the case that a plurality of patterns are arranged to be sewn, the operator must measure the size of the stitch pattern area and calculate a modification ratio, i.e., an enlargement or a contraction ratio of the arranged patterns to make the size of the pattern area close to that of the desired sewing region.
For another type, a pattern sewing machine having a CRT display is disclosed in U.S. Pat. No. 4,622,907. In this art, the size of the embroidery frame and the arrangement of the patterns to be sewn can be shown on the CRT display. This case, however, also requires the calculation of the enlargement/contraction ratio of the patterns to match the sewn pattern to the full extent of the sewing region.
In U.S. patent application Ser. No. 932,747 (now U.S. Pat. No. 4,742,786) bearing the same assignee as the present invention, which is filed on Nov. 18, 1986 and has been allowed, a kind of automatic modification system is described. The feature of this art is seen in an optional curve which is provided by an operator. Patterns to be stitched are automatically arranged along the curve so that the patterns extend from one end of the curve to the other end. However, this prior art describes only an automatic enlargement means but makes no mention of a contraction means.